1. Field of the Invention
This invention relates to a process for the preparation of thermoplastic graft copolymers and particularly a process wherein the graft copolymers are formed by reacting a trunk copolymer having reactive sites with a side chain polymer having an amine group reactive with the sites. This invention also relates to graft copolymers.
2. Description of the Prior Art
Many grafting processes are described in the prior art. Generally, the term "to graft onto" relates to a two step process whereby a polymerizable monomer is first blended with a polymer and then the monomer is polymerized, e.g., by free radical or ionic graft polymerization, in the presence of the polymer. In the conventional process this term to graft onto means a process in which the side chain polymer is grown in the presence of the dead or preformed polymer. In the conventional grafting process, electron irradiation, peroxide treatment, etc. are used to activate sites on the polymer chain for subsequent polymerization of the monomer and attachment to the sites. Typical of prior art relating such conventional grafting processes include U.S. Pat. Nos. 3,136,738; 3,388,186; 3,465,059; 3,676,190 and Belgian Patent Nos. 780,964; 780,965 and 780,966. U.S. Pat. No. 3,136,738 describes the grafting onto a vinyl backbone copolymer in the presence of catalysts a caprolactam. The polycaprolactam is grown as a side chain onto the backbone polymer at the active sites. U.S. Pat. Nos. 3,388,186 and 3,465,059 describe graft copolymers having backbone chains containing recurring ethylenic units and side chains containing carboxy-terminated polyamide groups, the graft copolymers being formed by hydrolytically polymerizing in the melt a polyamide precursor such as caprolactam or laurolactam in the presence of a preformed ethylene/acrylic acid, salt or ester copolymer. U.S. Pat. No. 3,676,190 discloses various type backbone polymers, preferably vinyl-type and vinylidene-type polymers and copolymers subjected to the action of ozone and onto the polymer is grafted at least one polymerizable ethylenically unsaturated monomer. The Belgian patents teach that random copolymers of ethylene and minor amounts of maleic anhydride can be reacted with alcohols and amines; for example, a polyethanol amine. These Belgian patents, however, describe bridged or crosslinked polymers where the bridging agents contain two or more reactive sites.
U.S. Pat. No. 3,676,400 relates to blends of high-amine-end polyamides with acidic olefin copolymers. The olefin copolymers can be derived from ethylene and monoethylenically .alpha.,.beta.-unsaturated monocarboxylic or dicarboxylic acids such as acrylic, methacrylic, maleic, fumaric acids, etc. Each polyamide molecule has on the average more than one active amine site which can react with the reactive sites of the trunk copolymer if such reactive sites are present. The reaction product contains crosslinks which are not desired in the graft copolymers of the present invention.
None of the prior art suggests grafting onto a trunk copolymer a preformed side chain polymer having one amine group active with sites on the trunk copolymer to produce a thermoplastic or soluble polymer.
The value of the present invention can be more fully understood when graft copolymers having two different types of side chains are prepared. If conventional prior art techniques are used, either copolymer side chains are obtained from mixed comonomers or when the monomers are used to form a graft copolymer in two steps either the active sites on the trunk copolymer are blocked by the first monomer or many side chains are formed containing grafts of the second monomer on the chains previously formed from the first monomer. In contrast, by the process described below, two or more types of side chain polymers may be grafted onto a trunk copolymer simply by mixing the preformed polymer side chains at the time the grafting reaction occurs.